Where can I find the original paper that introduced RNNs?
The two tech reports below both call RNNs explicitly &quot;recurrent net(work)s&quot;.

Rumelhart, David E; Hinton, Geoffrey E, and Williams, Ronald J (Sept. 1985). Learning internal representations by error propagation. Tech. rep. ICS 8504. San Diego, California: Institute for Cognitive Science, University of California.

Jordan, Michael I. (May 1986). Serial order: a parallel distributed processing approach. Tech. rep. ICS 8604. San Diego, California: Institute for Cognitive Science, University of California.


Jordan was a student of Rumelhart, so I would lean on identifying 1 as the paper introducing RNNs, with the caveat that the first sentence in the section &quot;Recurrent Nets&quot; of 1 reads:

We have thus far restricted ourselves to feedforward nets. This may
seem like a substantial restriction, but as Minsky and Papert point
out, there is, for every recurrent network, a feedforward network with
identical behavior (over a finite period of time).

This is interesting for two reasons:

After this sentence, he then goes on to show how RNNs can be unrolled and the error propagated back. Not a full-fledged BPTT yet, though.
The sentence shows that the idea of recurrence (and unrolling) has been around since at least 1969.

Unfortunately, I don't have access to Minsky and Papert (1969), so I cannot follow this line any further.